Parent.prototype.say = function () {
  console.log('hello');
}


function Parent(age) {    // 相当于Parent =new Function
  this.name = 'parent';
  this.age = age
}
Parent.say()


Child.prototype = new Parent()
function Child(name, age) {
  Parent.call(this, age);  // 继承 Parent 的属性和方法
  this.name = name;
}

const c = new Child('child', 50);
console.log(c.name);
console.log(c.age);
// c.say();



